Supernova Remnant Crossing a Density Jump: a Thin Shell Model

The environments of supernova explosion are often inhomogeneous and there may be jumps in their density structure. We have developed a semi-analytic model under the thin-shell approximation for supernova remnants that evolve crossing a density jump in the ambient medium. The generic evolutionary relations are presented for the blast wave after impacting on a cavity wall, which may be produced by the energetic stellar wind from the supernova progenitor. The relations can also be extended to the case that the blast waves break out from a dense cloud if different density contrast is used. This model is applied to N132D, a well-known cavity-born supernova remnant whose evolution has not yet been quantitively estimated in a cavity scenario due to lack of model formulae, and self-consistent physical parameters are obtained. Subject headings: ISM: bubbles — ISM: kinematics and dynamics — shock waves — supernova remnants — supernova remnants: individual: N132D